Heat exchanger baffle structure for air-heating furnaces



HEAT EXCHANGER BAFFLE STRUCTURE FOR AIR-HEATING FuRNAcEs Filed May 9, 1947 R. F. GIBLER Sept. 30, 1952 2 SHEETSj-'SHEET l Sept. 30, 1952 R. F. GIBLER 2,612,153

HEAT EXCHNGER BAFF'LE STRUCTURE FOR AIR-HEATING FURNCESl Filed May 9, 1947 2 SHEETS- SHEET 2 AL d J1 Patented Sept. 30, 1952 HEAT EXCHANGER BAFFLE STRUCTURE FOR AIR-HEATING FURNACES Roy F. Gibler, Cincinnati, Ohio; Madge Gibler, administratrix of said Roy F. Gibler, deceased, assigner of one-half to Grace Holmes, Cincinnati, Ohio Application May 9, 1947, Serial No. 746,886

7 Claims. (Cl. 126-110) This invention relates to furnaces and to heat exchangers for furnaces. More particularly it relates to an improved baie structure for use within a heating unit to catch and hold combustion gases in contact with heat exchange surfaces until the heat is removed therefrom by means of a fluid heat exchange medium.

One of the major sources of heat loss in furnaces occurs in the release of combustion gases through the stack while still hot. The exiting gases can carry with them a major portion of their heat. A principal objective of this invention has been to provide a construction for the internal portion of a furnace in which substantially all the heat carried by combustion gases is remved therefrom before the gases can leave the furnace.

A further objective of this invention has been to provide baiiles within a furnace which are constructed to hold the combustion gases until the heat has been extracted or transferred from them to the medium they are intended to heat.

A principal disadvantage of prior baiile structures for furnaces has been that the baffles have been so designed that they trap and hold dust and y ash carried in the combustion gases, which collect and build up heat insulating surfaces upon the baffles interfering with the proper flow of the combustion gases past the baiiles and insulating heat exchange surfaces of the baiiies to limit the amount of heat exchange possible. In accordance with this invention baffles having a self cleansing characteristic are provided in which dust and dirt do not collect upon the heat transfer surfaces. Briefly, this invention provides a plurality of baiiies having heat transfer surfaces inclined generally at an angle greater than the angle of repose of dust, ash, or soot contained in the hot gases to permit particles of dust etc, to roll downwardly under the influence of gravity. The lower edges of the baffles are spaced from the sides of a furnace box to provide space through which the particles can fall from the bailies into the bottom of the furnace box.

The bale structure is arranged to provide a tortuous path through which the hot gases flow and includes a series of peaked, trap baffles of inverted trough shape which may have a crosssection of inverted U-shape or inverted V-shape. Preferably, trap baflles of inverted V-shape are employed having sides inclined at an angle steeper than the angle of repose of dust particles. The bales are positioned within the furnace above the source of heat. Preferably, a gas or oil burner is employed but the baffles structure of this invention may be used to advantage with other types of heating units as well. Intermediate the trap baies are directive baiiles which cooperate therewith to guide hot gases into the trap baffles. The directive baiiies are maintained parallel to and spaced from and between the sides of the peaked trap baffles. The outer edges of the trap baffles are spaced from the sides of an inner furnace box while the outer edges of the straight directive bailies approach quite close to the sides of the furnace box without touching. The trap baffles serve to catch and hold combustion gases while heat is removed from them, and the directive baffles channel the gases into the trap baffles and prevent the gases from rising freely around the edges of the trap baiiles. The spaces between the lower edges of the directive baffles and the sides of the furnace box are suiciently narrow to inhibit the upward flow of hot gases yet sufficiently wide to allow particles of dust to fall freely therethrough.

As the heated combustion gases rise from the burner, they are caught and held in the peaks of the trap bafes. Only after the gases have cooled sufficiently to displace gases below them do the combustion gases trapped at the apex of each trap baffle settle downwardly and outwardlyto be removed from the battle. When the gases have flowed downwardly inside the bottom-most trap bale they ow outwardly around the ends and upwardly along its upper surfaces and below the directive baffles to be caught in the apex of the next higher trap bafe where the heat exchange cycle is repeated. Thus, the hot gases are forced to flow down as well as up and are prevented from escaping from the baiiles without delivering their heat to the heat exchange uid.

The baffles are attached to the sides of an inner furnace box and preferably are made of a hollow construction so that the heat exchange medium may be forced through the baffles as well as around the sides of the inner furnace box to pick up allthe heat of the combustion gases before the gases can be expelled from the furnace. The baffle structure of this invention may be employed with either a gaseous exchange medium such as air or4 a liquid heat exchange medium such as water and serves to conserve heat and prevent its dissipation until the heat exchange medium can pick it up.

Other objects and features of the` invention Will be apparent from the following description of the drawings which represent a preferred embodiment of the invention and in which is shown a furnace having a heat exchange containing bafflesV and constructed in accordance with this invention. Gas is the most expensive fuel commonly burned in furnaces and therefore it is necessary with gas to use the most effective heat transfer system. Hence, the invention is shown embodied in a furnace having a gas heating element. In the drawing:

Figure 1 is a side elevational view partly broken away and in section of a furnace constructed in accordance with this invention.

Figure 2 is an enlarged sectional elevational view taken along the line 2-2 in Figure l.

Figure 3 is an enlarged fragmentary sectional elevational view taken along the line 3--3 in Figure 2.

Figure 4 is a sectional elevational view taken along the same section line as Figure 3.

Figure 5 is a sectional plan view taken along the line 5-5 in Figure 4.

As illustrated in Figures 1 and 4 the furnace rests vupon a base IB. .The furnace includes an outer shell II, and an inner shell I2, between which shells air is circulated by means of a blower I3, .AirV is introduced into the furnace through, en; intake pipe. I4 and is .heated by beingl driven between the shells and through baffles in thel inner shell and thereupon forced from the furnace @relish heating. pipes I5. The heating pipesy |55.. are attached 11.0 the @eter shell I I by mearls. ef epprepriate. joints I6.-

A heating unit; .Il is leeeted. neer the bottom of the inner shell I2 and heated combustion gases from the heating unit I1 rise and are caught by trap baiiies I18-I of inverted V-shape, which are attached to and form a part of the m12?? Shfjl I2;

A s shown in Figure 2, the bafflesy I8, catch and held the, heated eembueien eases as they rise from the heating unit IlV until their heat is removed. Then thev gases flow downwardly and outwardly around the edges of the baffles I8 as shown by the arrows in Figure 2 and rise around the upper sides of` the trap boxes I8. Diagonal directive belliesr Ii) are provided. which parallel the sides ofthe trap baffles Iii. and channel the combustionV gases into and along the sides of the V-shaped trap baffles. When the heated combustion, gases` have risen4 fromv a lower trap baffle2l0i, they rise and are caught by an upper trap balile 2l where againl they are held andY trapped until heat is. removedv therefrom.

In more detail, the outer shell I I ofy the furnace is` constructed of. light sheet metal and, with the. inner shell, defines passages through which air may be. forced to pick up heat from the inner shell. Various heating,A pipes I5 of appropriate sizeare attachedtoand lead from the outer shell II.

The heating unit I1 is here shown constructed of a ring 22, which may burn gas as a fuel. I-Iowever,` if desired, an oil burner may be substituted for the gas ring shown without departing from the spirit of this invention. The gas ring 22 is connectedto andysupported by a gas pipe 23 whichpasses through theV inner.- and outer shells. Inspection doors 24 and 25.111n theouter andinner shells respectively permit inspection and` removal of theV burner ring 22. A. valve 2,6 on the gas pipe 2,31(shownschematically)y regulates the height of the gas flame. A mixing valve lll` (shownl schematically) adjusts the amountv of airdirected into the. furnace for use in supporting., combustion.

The `inner shell, which ispreferably constructed of. suitably heavy gauge, sheet metal, sections,

welded together, includes an upper half 28 and a lower half 29. The halves are equipped with attaching lips 30 and are joined together by a series of bolts 3 I. The inner shell is preferably constructed as shown in two sections for ease in handling, cleaning, and repair of the baille structure inside the inner shell.

Each half carries a trap baffle I8 and a pair 0f directive bailies I9 parallel to and spaced from the upper sides of the trap baille. All of the baffles are hollow, as clearly shown in Figure 2. A considerable space 32 separates each of the outer edges 33 of the trap bailies from the sides of the inner shell I2 and combustion gases ilow about the ends of the trap baies when rising through the inner shell. On the other hand, the directive baliies are spaced from the sides of the inner shell I2 by only small spaces 34, while the inner edges of the directive baflies I9 are separated by spaces 35 which are much larger than the spaces 34. Accordingly, the gases rising from the V-shaped trap baiiles. pass between the inner ends of the directive bales when rising and are directed into. the next higher trap bafe. However, any dirt, ash, or foreign matter which may become associated with the combustion gases cannot7 settle and build up on top of the baies but rather. falls downwardly through the small spaces 34. about, the outer edges of the directive baffles.. Thus, there is no accumulation of dirt. and ash upon the. bafiies which mightimpair heat. exchange and lower the efciency of the furnace,` and all dirt, ash, and foreign matter settles below the. baffles. Dirt, etc. which has settled to. the bottom of the inner shell can be removed at. intervals. through the inspection doors 24 and 25.

The bales I8. and I9, run lengthwise of, the furnace as shown in Figure 4r and are welded. to. the ends of the inner shell so that, each baille has open ends through which air, which, is the heat exchange fluid employed in the. unitv illustrated, is circulated as. shown by the arrows in Figure 4.

Combustion gases, after leaving. 'the upper trap baille 21| pass out of the inner shell, through a pair of smoke pipes` 3,6; The smoke` pipes 3.6. are located near the; right handV end ofthe. inner. shell as shown in Figure 4,. while. the, heating unit II is located. near and 'under theleft hand.

end of the inner shell.Y Thus, before, combustion gases can leayfev the inner shell they. must. rise throughy the inner, shell being. caught. and held by each trap baiilein turn and additionally must flow the. length, of the. shellbeflorebeingc removed from the, fiilinacefthro'ugh the. smoke pipes.

The` lower right,l hand corner. of, the inner shell` I2 is eut awmas. shown. at 3:1 in. rieure 4, to provide a space. in. which, the blower It is. located. Air to. the, blower I3, is, introducedthrough an intake pipe I Il. The, blower L3 is here shownV 'as a. centrifugal', type blowen It discharges air againstthe right. handwall; 3K of the outer shell. I I. 'I-The.. air. drive-n. by the blower is forced around' all sides, of., the, inner shell I2, over the top thereof and through., the hollow bamesv I8j andV i9; 'Ijhe baliles., are all' welded in placein thefurnace. and; because of. the good heat conducting properties of'therela.- tively heavy sheet metal of whichY the. inner. shell is constructed, heat transferred to the bales need not all be absorbed by ail; passingl through the bales.. ,The conducti'onofiheat from. the.; baies to the outer walls of' the inner shell makes it possible for the air driven around'the sides and over the top of the inner shell l2 to pick up heat as well as the air driven through the inside of the hollow baffles.

The furnace illustrated in the drawings ris shown equipped with a gas burner as the source of hot gases. As a safety measure a manifold 40 (Figure 2) is provided which by-passes the V-shaped baiiles. The manifold 40 is constructed of a pipe 4| having angular ends 42 and 43 which project into the inner shell l2 respectively below and above the trap baffles. A short pipe lill leads from below the upper trap baiiie into the manifold 40. The manifold serves to lead gas around the bales and into the smoke pipes St in case the burner becomes extinguished. A connection 45 is provided in the pipe 4| and makes it `possible to remove the upper half of the inner shell from the lower half.

The baiile structure of the present invention permits the maximum economy in the use of fuels which do not require a powerful draft to cause combustion. The combustion gases are caught by the trap baffles and held in the peaks of each until suiicient heat has been removed therefrom that the gases will have cooled until the gases along the lower portions of the baflie can be displaced. Only after the combustion gases have cooled sufficiently to displace the gases which are below can they escape. Then the gases are led and channeled between the upper surfaces of the trap baffles and the directive baffles It to be caught and held by the next higher trap baffles. This construction makes it possible to permit the gases rising through the smoke pipe to have a temperature only a small amount above room temperature. v

The furnace herein shown utilizes air as its medium for the transfer of heat. However, other heat transfer uids may be employed. More particularly, liquids such as water may be led or pumped through the baiiie structure instead of air, and the invention is not intended to be limited by the foregoing description of a preferred embodiment except as pointed out in the appended claims.

Having described my invention, I claim:

1. A heat exchange unit comprising; an outer shell, an inner shell disposed within the outer shell in spaced relationship therewith, a source of combustion gases located adjacent the bottom of the inner shell, a plurality of hollow baiiles of inverted trough shape in cross section extending across said inner shell above the source of combustion gases with the opposite ends of the baffles communicating with the space between the inner and outer shells,a plurality of hollow directive baffles interposed between said inverted trough shaped baflies and spaced vertically with respect to them to delineate a tortuous passageway for rising combustion gases and to direct said rising combustion gases to the undersides of the trough shaped baiiies, and means for circulating a heat transfer fluid through the outer shell to exchange heat through said baffles.

2. A heating unit comprising; an outer shell, an inner shell disposed within the outer shell in spaced relationship therewith, a plurality of hollow heat exchange bailies extending across said inner shell, a source of combustion gases located within the lower portion of the inner shell, and a manifold tube having pa-ssageways extending through the inner shell below and above the baffles and adapted to bypass a regulated volume of combustion gases around the bales.

3; A heating unit which comprises an outer' shell, an inner shell contained within said outer shell, walls of said inner shell being spaced from walls-of said outer shell, a plurality of trap baffles mounted inside said inner shell, said baiiles being of peaked shape and mountedy in spaced vertical relationship, said baffles being hollow and being lattached to frontand rear ends of said inner shell, the hollow spaces in said baiiles communieating with the space between said shells, a source of combustion gases within said inner shell and below said plurality of baflies, and means for circulating a heat transfer fluid between said shells and through said baffiesto recover heat from said combustion gases.

4. A heating unit which comprises an outer shell, an inner shell contained within said outer shell, the walls of said inner shell being spaced from the walls of said outer shell, a plurality of baffles mounted within said inner shell, said baffles `being of peaked shape and mounted in spaced vertical relationship, and being attached to front and rear ends of said inner shell, a g'as burner Within said inner shell and below said peaked baffles, whereby hot combustion gases rise and are caught and held in the peaked baflies until heat is removed therefrom, and a manifold tube having its lower end connected to the inner shell below said baffles and its upper end connected to the shell above the baiiles to bypass a controlled volume of combustion gases past the bafiies.

5. A heating unit which comprises an outer shell, an inner shell contained within said outer shell, the walls of said inner shell being spaced from the walls of said outer shell, a plurality of heating pipes connected to and leading from said outer shell, a plurality of baiiles mounted within said inner shell, said bailies being of inverted V-shape and mounted in spaced vertical relationship, the outer edges of said baffles being spaced from the sides of said inner shell to permit the flow of combustion gases about the ends of said baffles, a plurality of directive baffles parallel to and spaced from the sides of the V-shaped baffles, the inner edges of the directive baffles being spaced to permit the ow of combustion gases, the outer edges of said directive baiiles being spaced from the edges of the inner shell to permit finely divided solid matter in the combustion gases to fall through said inner shell, a source of combustion gases within said inner shell and mounted below said baiiles, whereby combustion gases rise and are caught and held in the peak of the lowest V-shaped baffle until heat is removed therefrom and thereupon flow downwardly and upwardly to be caught by succeeding higher V-shaped baiiies, said baffles being hollow, and means for circulating a heat transfer uid between said shells and through said hollow baffles into said heating pipes to remove heat from the heating unit.

6. A heating unit which comprises an outer shellan inner shell contained within said outer shell, the walls of said inner shell being spaced from the walls of said outer shell, a plurality of heating pipes connected to and leading from said outer shell, a plurality of baiiies mounted within said inner shell, said baffles being of inverted V-shape and mounted in spaced vertical relationship, the outer edges of said baies being spaced from the sides o-f said inner shell to permit the flow of combustion gases about the edges of said baiies, a plurality of directive baiiles parallel to and spaced from the sides of the V-shaped bailles, the inner edges of the directive baflies being spaced to permit the ilow of combustion gases, the outer edges of the directive batlies being spaced from the sides of the inner shell to permit finely divided solid matter in the combustion gases` to fall through said inner shell, a source of combustion gases Within said inner shell and mounted below said ballles, whereby combustion gases rise and. are caught and held in the peak 0f the lowest v-shaped baille until heat is removed therefrom., and thereupon ow downwardly and upwardly to be caught by succeeding higher V-shaped baffles. said ballles being hollow, and a blower adapted to circulate air between said shells and through said hollowV baliles into said heating pipes to remove heat from the heating unit.

7. A heat exchange unit comprising a shell, a source lof combustion *gases adjacent the bottom of the shell, a plurality of hollow trap baffles of inverted trough shape vmounted above said source of combustion gases, a plurality of hollow direcvv tive baffles mounted substantially parallel to the sides of said trap baliles., means for circulating a heat transfer fluid through the hel-low'V trap baiiles and the hollow directive ballles, the louter edges of the trap baiiles bein-g spaced from the walls of the shell, the outer edges of the directive baies being spaced from the walls of the shell a lesser distance than the edges'` of said trap baies, and said trap bales being disposed verti-` cally between the directive bales, whereby rising combustion` gases are channelled by sa-d directive baffles into said trap ball'es' and held in said trap baiiies until heat is removed therefrom by the heat trans-fer fluid. Y

'ROY F. GIBLER.

REFERENCES vCITED The following references are of record ign the le of this' patenti' UNI-TED STATES 100,107 Bellman Feb. 22, 1870 638,708 Hansen Dee.v 12, 1899 1,076,209 Kent Oct. 211, 1913' 1,689,067 Benner 061i. 23,l 11928 FOREIGN PATENTS Number Country Date 6,272' Great' Britain Mar. 26, 1895V 

